Kyong Nam Kim

Characteristics of Parallel Internal-Type Inductively Coupled Plasmas for Large Area Flat Panel Display Processing

The development of a large-area high-density plasma source is desired for various plasma processes from microelectronics fabrication to flat panel display (FPD) device fabrication. In this study, using a parallel internal-type (double comb-type) inductively coupled plasma source having the size of 1020 mm×830 mm, high density plasmas on the order of 2.2×1011 cm-3 could be obtained with Ar at 5000 W inductive power. Plasma uniformity on the substrate in the size of 920 mm×730 mm decreased with the increase in inductive power and was about 8% when the inductive power was 5000 W. When SF6 was used to etch SiO2 using the source, the SiO2 etch rate higher than 2000 A/min with an etch uniformity of about 6% could be obtained at 5000 W inductive power, -350 V bias voltage, and 15 mTorr operating pressure.

A Study of Sapphire Etching Characteristics Using BCl3-based Inductively Coupled Plasmas

Cl2, HCl, and HBr added BCl3-based inductively coupled plasmas were used to etch (0001) sapphire wafers and their etch characteristics were investigated. The plasma characteristics were monitored in-situ by optical emission spectroscopy and a Langmuir probe. A photoresist was used as the etch mask and an etch selectivity greater than 1 with the etch rate of 3800 ?/min could be obtained with 20%HCl/80%BCl3. The most anisotropic etch profile could be observed in 10%HBr/90%BCl3.

Uniformity of internal linear-type inductively coupled plasma source for flat panel display processing

The variation in plasma uniformity over an extremely large size inductively coupled plasma (ICP) source of 2750×2350mm2 was examined. An internal linear-type antenna called “double comb-type antenna” was used as the ICP source. A plasma density of ∼1.4×1011∕cm3 could be obtained at 5mTorr Ar by applying 10kW rf power to the source at a frequency of 13.56MHz. An increase in rf power from 1to10kW improved the plasma uniformity over a substrate area of 2300×2000mm2 from 18.1% to 11.4%. The improvement in uniformity of the internal ICP source was attributed to the increase in plasma density near the wall.

Effective plasma confinement by applying multipolar magnetic fields in an internal linear inductively coupled plasma system

A novel internal-type linear inductive antenna referred to as “double comb-type antenna” was used for a large-area plasma source with the substrate area of 880mm×660mm and the effect of plasma confinement by applying multi-polar magnetic field was investigated. High-density plasmas on the order of 3.18×1011cm−3, which is 50% higher than that obtained for the source without the magnetic field, could be obtained at the pressure of 15mTorr Ar and at the inductive power of 5000W with good plasma stability. The plasma uniformity less than 3% could also be obtained within the substrate area. When SiO2 film was etched using the double comb-type antenna, the average etch rate of about 2100A∕min could be obtained with the etch uniformity of 5.4% on the substrate area using 15mTorr SF6, 5000W of rf power, and −34V of dc bias voltage.

Selective Etching of Magnetic Tunnel Junction Materials Using CO/NH3 Gas Mixture in Radio Frequency Pulse-Biased Inductively Coupled Plasmas

To enhance the volatility of etch products and to increase the etch rates of MTJ materials, other techniques such as substrate heating and source power RF pulsing have been also investigated. 26–28) The study on the effect of substrate temperature during the etching of the MTJ materials using CH3OH in an ICP showed that, with the increase of substrate temperature from 20 to 120 � C, the deposition of sidewall residue was decreased while the etch rates of MTJ materials were increased. In the case of etching the MTJ materials using the pulsing of microwave plasma in Cl2-based gases (source power pulsing not bias power pulsing), high etch rates of MTJ materials without corrosion or delamination were observed, while corrosion and delamination of MTJ materials were observed in the etching using continuous wave (CW) microwave plasmas. The researchers believe that the negative ions formed during the power-off period enhance the chemical reactions on the surface of magnetic films. They reported that the magnetic characteristics were also significantly improved by using the source powerpulsed plasma because of reduced residues in addition to the improvement of the etch profile. 29)

Mass spectrometric study of discharges produced by a large-area dual-frequency–dual-antenna inductively coupled plasma source

An energy-resolved quadrupole mass spectrometer is used to investigate the time-averaged ion energy distribution (IED) of positive ionic species in an Ar/CF4 (90%/10%) discharge produced by dual-frequency?dual-antenna, next-generation large-area inductively coupled plasma source. The operating pressure is 10?mTorr. Two radio frequencies of 2?MHz (low frequency) and 13.56?MHz (high frequency) are used to initiate and sustain the discharge. The orifice of the mass spectrometer was 100??m in diameter and placed at 30?mm below the ICP source and 20?mm outside the discharge volume.It is observed that both of the frequencies have significant effect on IEDs of all prominent discharge species. The evolution of IEDs with power shows that the discharge undergoes a mode transition (E to H) as the applied power is increased. At a fixed value of P13.56?MHz (250 and 500?W), the energy spread and the energy separation between two peaks of IEDs increase illustrating enhanced E-mode. Above P13.56 MHz?=?500?W, the IEDs show opposite trends, i.e. decreasing energy spread and energy separation between two peaks, showing the strengthening of H-mode. Increasing P13.56?MHz at a fixed value of P2?MHz has similar effects. A comparison of IEDs sampled at a fixed total power (P13.56 MHz?+?P2 MHz) demonstrates that an IED can be tailored by changing the power ratio (P13.56?MHz/P2?MHz).

Modulation of electron energy distributions and discharge parameters in a dual frequency ICP discharge

Using a radio frequency (RF) compensated Langmuir probe, modulations in electron energy distribution (EED) and plasma potential are investigated in a discharge produced by a large-area dual frequency/dual antenna inductively coupled plasma source. The discharge is ignited using two frequencies (2 and 13.56 MHz). It is observed that the EEDs can be tailored by varying the power ratio of the two frequencies. Increasing the power level of the low frequency (P2 MHz) enhances the population density of high-energy electrons; however, increasing the high-frequency power (P13.56 MHz) increases the low-energy electron population density. At a fixed total power (P2 MHz + P13.56 MHz), the higher the low-frequency power (P2 MHz) content, the higher the population density of high-energy electrons; however, this trend reverses with high-frequency power (P13.56 MHz). The influence of power ratio on plasma density (ne), plasma temperature (Te) and plasma potential (Vp) has also been studied. It is found out that the plasma parameters have similar trends with RF power irrespective of its frequency. The value of ne increases, and Te and Vp decrease with increasing power. At a fixed P2 MHz, Vp increases with increasing P13.56 MHz. However, Vp decreases with increasing P2 MHz at a fixed value of P13.56 MHz.

Novel internal linear inductively coupled plasma source for flat panel display applications

In this study, using two different types of linear internal type inductively coupled plasma sources with a serpentine-type antenna and a novel double-comb type antenna having the size of 1020×830 mm2, the characteristics of their plasmas were compared as the application to the flat panel display manufacturing. The use of the double-comb type antenna instead of the serpentine-type antenna showed two times higher plasma and radical densities, and more stable plasma when rf power higher than 2000 W was applied. By the application of 5000 W of rf power with 15 mTorr Ar, a high plasma density of 2.2×1011/cm3 with the plasma uniformity of 8% could be obtained for the double-comb type antenna. The increase of plasma density, radical density, and plasma stability for the double-comb type antenna compared to the serpentine-type antenna appears from the higher inductive coupling and less standing wave effect compared to the serpentine-type antenna.

Plasma Characteristics of Inductively Coupled Plasma Using Dual-Frequency Antennas

The plasma characteristics of inductively coupled plasma (ICP) sources operated with dual-frequency antennas with frequencies of 2 and 13.56 MHz were investigated and compared with a source operated with a single-frequency antenna at 13.56 MHz. Improved plasma characteristics such as higher plasma density, lower plasma potential, and lower electron temperature were observed with the dual-frequency ICP source owing to the high absorbed power through the lower driving of the frequency antenna. Also, the variation of the dual-frequency power ratios changed the electron energy distribution. Therefore, when silicon was etched using the dual-frequency ICP with CF4/Ar, the maximum etching selectivity of silicon over the photoresist could be observed at a 2 MHz rf power ratio of approximately 70% possibly due to the different gas dissociation characteristics for different dual-frequency power ratios, even though the etching rate of silicon increased with the 2 MHz power ratio owing to the increased plasma density. In addition, by using the dual-frequency ICP antennas instead of the single-frequency antenna, the plasma uniformity was also improved.

Line-type inductively coupled plasma source with ferromagnetic module

The characteristics of a line-type, internal antenna for an inductively coupled plasma (ICP) source installed with a ferromagnetic module were investigated for possible application to roll-to-roll processing of next-generation display devices. The use of 2 MHz instead of 13.56 MHz for the 2300 mm long ICP source improved the plasma uniformity to less than 11% along the antenna line. In addition, the use of Ni–Zn ferromagnetic material in the line-type antenna improved the plasma density to about 3.1 × 1011 cm−3 at 3500 W of 2 MHz radio frequency power by confining the induced, time-varying magnetic field between the antenna line and the substrate. When the photoresist-covered glass substrate was etched at 4000 W using 40 mTorr and Ar/O2 (7 : 3), an etch uniformity of about 5–6% was obtained along the antenna line.